Method and apparatus for controlled dopant incorporation and activation in a chemical vapor deposition system

Abstract

Embodiments include systems and methods for producing semiconductor wafers having reduced quantities of point defects. These systems and methods include a tunable ultraviolet (UV) light source, which is controlled to produce a raster of a UV light beam across a surface of a semiconductor wafer during epitaxial growth to dissociate point defects in the semiconductor wafer. In various embodiments, the tunable UV light source is configured external to a Metal Organic Chemical Vapor Deposition (MOCVD) chamber and controlled such that the UV light beam is directed though a window defined in a wall of the MOCVD chamber.

Description

TECHNICAL FIELD[0001]Embodiments relate to processes or apparatuses specially adapted for the manufacture or treatment of semiconductor or solid-state devices or of parts thereof. More specifically, embodiments relate to using reduction or decomposition of a gaseous compound yielding a solid condensate (i.e., chemical vapor deposition or Metal Organic Chemical Vapor Deposition (MOCVD)), and bombardment of such structures with optical radiation during manufacture.BACKGROUND[0002]Chemical vapor deposition involves directing one or more gases containing chemical species onto a surface of a substrate so that the reactive species react and form a deposit on the surface. For example, compound semiconductors can be formed by epitaxial growth of a semiconductor material on a substrate. The substrate typically is a crystalline material in the form of a disc, commonly referred to as a “wafer.” Compound semiconductors such as III-V semiconductors commonly are formed by growing layers of the co...

AI Technical Summary

Benefits of technology

This patent describes a method for growing semiconductor layers with reduced point defects. The method involves positioning a wafer in a chamber and applying a gas mixture to cause the semiconductor layer to grow epitaxially on the wafer. While applying the gas mixture, a UV beam of light is directed onto the semiconductor layer using a rastering system to create a pattern. The UV beam is tuned to dissociate point defects in the semiconductor layer. This method can be used to make semiconductor devices with better quality layers.

Problems solved by technology

These point defects can become incorporated into the crystal structure of the GaN semiconductor during growth, leading to passivation or compensation of Mg acceptor levels.

Passivation or compensation of the dopant reduces the overall electrically active dopant levels, which is generally undesirable.

However, these post-growth annealing procedures are inefficient, both in terms of time of production and energy costs.

In addition, they add an extra thermal budget to the existing epitaxial structure growth process.

This added thermal exposure can result in solid-state diffusion of dopants or alloy constituent atoms, thereby resulting in less controlled, abrupt compositional and doping junctions

Although this initial research identifies a possible mechanism for reducing the number of Mg—H, VN, or VN—Mg point defects and complexes, implementation remains challenging for at least three reasons.

First, large volume production MOCVD processes are typically conducted in chambers that do not facilitate light ingress or have internal light sources.

Second, even if a suitable mechanism were found to provide light to the interior of the MOCVD reactor, irradiating the entire wafer with UV light during the epitaxial growth process would be energy intensive over such a large deposition area.

Third, operating the light source at a low energy level may be insufficient to dissociate all point defect complexes, while operating the light source at high energy could cause undesirable reactions between the residual MOCVD gases / vapors in the chamber, and the minimum and maximum acceptable energy levels for the applied light can change based on the precursors used in the MOCVD process.

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